Professor Sarah Perry of the Chemical Engineering Department is part of a research team from the University of Massachusetts Amherst and the University of Illinois Urbana-Champaign that has discovered how to read patterns of charges on long polymer molecules that determine their function and direct their shape. See Inside UMass article: Perry Helps Decode How Charge Patterns Instruct Polymer Chain Functions . See media coverage: Phys.org, Science Codex, Science Daily, Tech Explorist.
The findings, published in the journal ACS Central Science, allow scientists to predict quickly and accurately how the polymers will act and will help them design new materials using specific charge sequences.
Perry says that nature uses long-chain molecules called polymers for a diverse array of applications. For example, proteins are used to build tissues, enzymes perform chemistry, and DNA encodes the information of life. In most of these examples, the polymer is folded into a complex shape that defines its function. It is that process that Perry and her colleagues set out to understand.
As Perry explains, “In the current article [ACS Central Science], which builds on the results of our earlier Nature Communications paper, researchers in my lab collaborated with the group of Charles Sing [at Illinois Urbana-Champaign] to understand how the sequence of charge along a model polymer affected its ability to create self-assembling liquid materials. These self-assembled liquids, also known as ‘complex coacervates,’ are directly analogous to increasing numbers of liquid granules being discovered in cells.”
The Perry Research Group utilizes self-assembly, molecular design, and microfluidic technologies to generate biomimetic microenvironments to study and enable the implementation of biomolecules to address real-world challenges
Perry says that the polymers found in nature are in stark contrast to most applications of polymers or plastics that we see in our everyday life. However, scientists are increasingly discovering new examples in which biology makes use of unstructured or intrinsically disordered proteins or polymers.
“In these examples, the function of the protein is still defined by the sequence of chemistry encoded along the polymer chain,” Perry says, “but we need a new way of understanding how this molecular-level information is translated into function.”
According to the abstract of the ACS Central Science article, charged polymers are ubiquitous in biological systems because electrostatic interactions can drive complicated structure formation and respond to environmental parameters such as ionic strength and pH. In these systems, function emerges from sophisticated molecular design.
However, as the abstract makes clear, the role of a charged monomer sequence in dictating the strength of electrostatic interactions remains poorly understood despite extensive evidence that sequence is a powerful tool biology uses to tune soft materials.
“In this article,” the researchers say, “we use a combination of theory, experiment, and simulation to establish the physical principles governing sequence-driven control of electrostatic interactions.”
The researchers add that “We predict how arbitrary sequences of charge give rise to drastic changes in electrostatic interactions and correspondingly phase behavior…This work thus provides insights into both how charge sequence is used in biology and how it could be used to engineer properties of synthetic polymer systems.”
Perry concludes that “Our experimental results, coupled with theory and simulation results from the Sing lab, have firmly identified the ways in which charge patterning can affect these materials. Furthermore, we have demonstrated a new method for quickly predicting the phase behavior of these materials to aid in future materials design efforts.” (June 2019)